[RFC PATCH v0.2] PCI: Add support for tango PCIe host bridge
slash.tmp at free.fr
Mon Mar 27 12:44:08 PDT 2017
On 27/03/2017 19:09, Marc Zyngier wrote:
> On 27/03/17 16:53, Mason wrote:
>> I have one remaining issue with bitmaps.
>> My HW regs are 32b. How do I grab e.g. bits 96-127?
>> All I can think of is
>> u32 val = ((u32 *)bitmap);
>> Is this acceptable?
>> mrutland mentioned bitmap_to_u32array() but IIUC it is used to
>> copy an entire bitmap.
> The real question is "Why do you need such a thing?".
You told me to use an in-memory version of the "unmasked"
bitmap, yes? In that case, I need to be able to grab
a piece of said bitmap, to update the corresponding piece
of the HW bitmap.
For example, assume the first 3 MSIs are unmasked,
in other words, unmasked = 0x7
A new user comes along and wants to assign an MSI.
Scan "unmasked", found bit at pos 3.
Update "unmasked" to 0xf.
At some point, I need to write 0xf to some HW reg.
So I need to grab a piece of "unmasked" (bits 0-31 in my example)
pos = find_first_zero_bit(unmasked, COUNT);
int reg_index = pos / 32;
u32 val = ((u32 *)unmasked)[reg_index];
writel_relaxed(val, pcie->enabled + reg_index * 4);
Or did I miss something in your suggestion?
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